Facing a feisty crowd of constituents who shouted, interrupted and shook their heads at him, freshman Rep. Frank Guinta, R-N.H., spent two hours Thursday night calmly defending his vote for a GOP-led plan to overhaul the country's Medicare system.

"Why Congressman Guinta, why in the world, did you ever vote for the Paul Ryan Medicare plan," asked, Gary Patton, who posed the first question at an often raucous town hall meeting the congressman hosted at a local high school here.

Patton, 73, told Guinta that he was concerned that the plan introduced by Rep. Paul Ryan, R-Wis., the chairman of the House Budget Committee, would "end Medicare as we know it."

"The proposal that was in the House last week, again, does not affect anyone who is 55 or older," Guinta assured. "I want to try to allay some fears about the proposal, I want to make sure that people have the proper information. If you don't like the plan, let me know that."

Someone shouted back: "We don't like it!"

Guinta, who rode the Tea Party wave to Washington last year, is one of many new lawmakers who are now facing difficult questions from voters back at home as they wrestle with how to deal with the country's rising debt and whether to make sweeping changes to entitlement programs like Medicare.

"Congressman Guinta is very smooth, he's very slick," Patton, a retired resident of Hampton, N.H., said in an interview with ABC News after the town hall meeting, adding that he was not satisfied with the congressman's answer to his question.

Patton wasn't the only one.

Joe Platte, a middle school student from nearby Stratham, N.H., who took a back-row seat at the meeting, interjected: "What about me? I'm 14, what am I going to do."

The contentious gathering of more than 100 Seacoast residents did not appear to catch Guinta by surprise. He handled the combative crowd gingerly, emphasizing his desire to "find common ground" even with those who disagree with him.

He plowed through more than a dozen questions on issues ranging from ethanol subsidies ("we ought to do away with it, pure and simple," he said) to the national debt.

He took an I-feel-your-pain approach to the issue of rising gas prices, telling his constituents that he recently filled up the tank of his Ford Edge.

"I filled up last night and it cost me $71.50," he said. "To have almost $4 a gallon gas, I think affects every single one of us in this room."

At several points Thursday night, however, Guinta could not deliver complete answers without interruptions from the crowd. "I would like to finish my statement," the House freshman said amid a mix of cheers and boos when one member of the audience declared that President Obama "doesn't give a damn about reducing spending."

"I understand that there is a lot of passion and a lot of emotion -- it's why this job is so important right now," Guinta said. "Let's put our energy on things we can agree to rather than divide the country farther."